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Vector Algebra question

2010 · Shift 2 · Q38

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PYQ Library
JEE Advanced
Mathematics
Vector Algebra
2010 · Shift 2 · Q38

Vector Algebra question

2010 · Shift 2 · Q38

JEE AdvancedMathematicsVector AlgebraMCQ+4 / −1

Two adjacent sides of a parallelogram

ABCD

are given by

\overrightarrow {AB} = 2\widehat i + 10\widehat j + 11\widehat k

and

\,\overrightarrow {AD} = -\widehat i + 2\widehat j + 2\widehat k

The side

AD

is rotated by an acute angle

\alpha

in the plane of the parallelogram so that

AD

becomes

AD'.

If

AD'

makes a right angle with the side

AB,

then the cosine of the angle

\alpha

is given by

A
${{8 \over 9}}$
B
${{{\sqrt {17} } \over 9}}$
C
${{1 \over 9}}$
D
${{{4\sqrt 5 } \over 9}}$

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